Climate change: A warming Arctic is pushing the jet stream further south

As the Arctic warms, changes in air pressure and circulation are pushing the jet stream farther south, according to the National Oceanic and Atmospheric Administration’s Arctic report card, released last week. The changes were especially noticeable inDecember 2009,when the normal climate pattern reversed. Higher pressures over the Arctic eliminated the normal west-to-east jet stream winds. That allowed cold air from the Arctic to penetrate all the way into Europe, eastern China, and Washington DC. As a result, December 2009 and February 2010 exhibited extremes in both warm and cold temperatures with record-setting snow across lower latitudes…,/p>

The changes in circulation include an unprecedented southerly wind flow from the Bering Strait across the North Pole. The Arctic Dipole Anomaly, as it’s been dubbed, was evident for the first time in 2007, when Arctic sea ice was at an all-time record low. The same wind pattern developed again in May and June 2009 and 2010. The NOAA scientists were cautious to say that individual weather extreme events cannot be directly linked to larger scale climate changes. But recent data analysis and modeling suggest a link between loss of sea ice and a shift to an increased impact from the Arctic on mid-latitude climate. “With future loss of sea ice, such conditions as winter 2009-2010 could happen more often, the report card concludes. “Thus we have a potential climate change paradox. Rather than a general warming everywhere, the loss of sea ice and a warmer Arctic can increase the impact of the Arctic on lower latitudes, bringing colder weather to southern locations.”